1. Field of the Invention
This invention relates to implantable medical devices, such as stents, and a method of resolving ischemia by inducing formation of new blood vessels through angiogenesis and arteriogenesis.
2. Description of the Background
A major component of morbidity and mortality attributable to cardiovascular disease occurs as a consequence of the partial or complete blockage of vessels carrying blood in the coronary and/or peripheral vasculature. When such vessels are occluded, various complications may result from death of tissue previously nourished by the occluded vessels or inability of the occluded vessels to transport sufficient blood supply to regions requiring high blood consumption and accompanying nutrients.
Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels. Such mechanical enhancements are often provided by employing surgical techniques that attach natural or synthetic conduits proximal and distal to the areas of occlusion, thereby providing bypass grafts, or revascularization by various means to physically enlarge the vascular lumen at the site of occlusion. These revascularization procedures involve such devices as balloons, endovascular knives (atherectomy), and endovascular drills. The surgical approach is accompanied by significant morbidity and even mortality, while the angioplasty-type processes are complicated by recurrent stenoses in many cases.
In some individuals, blood vessel occlusion is partially compensated by the natural process of therapeutic angiogenesis, in which new vessels are formed to replace the function of the impaired vessels. These new conduits may facilitate restoration of blood flow to the deprived tissue, thereby constituting “natural bypasses” around the occluded vessels. However, some individuals are unable to generate sufficient new vessels to adequately compensate for the diminished blood flow caused by cardiovascular disease. Accordingly, it would be desirable to provide methods and systems for delivering agents to help stimulate the natural process of therapeutic angiogenesis in occluded coronary and peripheral arteries in order to treat ischemia.